Throughout the years, we’ve looked at a lot of great engines on this website, but today we’re doing the exact opposite and going through some of the worst engines in automotive history. There’s a little bit of everything in here, and the last engine on the list will definitely surprise you, so let’s get into it.
As a quick preface, I think it’s worth mentioning that there is no perfect of quantifying what makes an engine good or bad.
And realistically, there are lots of bad engines out there that have loads of problems, such as the BMW N54, but an engine like that has so many pros compared to the cons that it wasn’t added to the list.
Every engine we’re about to list is an engine with lots of cons and minimal pros, so keep that in mind.
#1 Cadillac Northstar V8
What better place to start this list than with one of GM’s biggest failures ever in the Cadillac Northstar V8. This engine came about in 1992 when Cadillac had gotten sick of being bullied by German automakers producing vastly nicer cars with extremely smooth engines that were selling like hotcakes.
And with this engine, Cadillac’s idea was simple, embrace the future of overhead cams as the superior option to a cam-in-block engine. And while Cadillac was definitely right that, on paper, an overhead cam V8 engine is superior to an overhead valve V8 engine, their execution of the idea was, well, not fantastic.
On paper, though, this was super impressive at the time that it came out, with a whopping 295hp and 290lb-ft of torque from a naturally aspirated 4.6L engine (numbers from the Eldorado Sport Coupe). That was about as much power as the Corvette from the same year with its much larger 5.7L engine.
So what’s wrong with this engine, you might be asking? Basically everything. Sort of. For one, head gasket failure is reported as fairly common, as is alarming oil consumption and burning. There was a Cadillac service bulletin going over this, with the cure coming in the form of a piston ring cleaning procedure with a GM four-step engine cleaning kit that you can still order to this day.
There are also issues on the later Northstar V8 engines of excessive carbon buildup causing a knock on cold starts, no oil pressure on some of the older engines, leaky rear main seals, and more. Hell, GM even noted that a quart of oil per 1,000 miles was normal for this engine.
And just as a side note, this engine was listed as one of the ten best engines in North America by Ward’s when it was new, highlighting just how meaningless those awards truly are.
#2 6.0L Powerstroke
And what terrible engine list could ever be complete without mentioning the god-forsaken Ford 6.0L Powerstroke. God, I love hating on this engine, and I love seeing boneheads try to defend it.
This engine was born out of a need for a newer engine as the 7.3L Powerstroke could no longer meet the emissions and power output required for the F250 and F350 to compete with what GM and Dodge were offering with their trucks.
Compared to the 7.3L Powerstroke, the 6.0L was a big jump in terms of performance and emissions. A few key features include the four-valve cylinder heads, a quick-spooling variable geometry turbocharger, a lower voltage and higher-pressure version of the HEUI injection system, and a crankcase bed plate for superb bottom end strength.
But none of that really mattered in the long run because just about all of those advancements turned into massive problems.
The problems start at the EGR cooler, with is known for cracking and/or clogging, both of which can and will cause even further problems. Then there’s the EGR valve which is known for sticking.
Then you have the oil cooler, which can get clogged up from sand in the coolant system left over from when the block was originally cast in the factory.
On top of that, there are a lot of instances of high-pressure oil pump failure, which then means your truck literally won’t run because the injectors rely on high-pressure oil in order to operate, which is then compounded even further with the low-pressure oil pump issues.
And worst of all, the entire engine is filled with small gaskets and o-rings to hold the high-pressure oil system, which means you can have failures in lots of little places that will cause the entire engine to not run or at least to hard start every time you fire it up.
On top of all, the torque-to-yield head bolts are too skinny to hold anything past stock boost levels and will stretch, resulting in head gasket failures.
While Ford guys are right to say that the 6.0L’s issues are made worse when you crank the power up, they’re wrong to call the detuned International VT365 found in industrial applications a “reliable” engine. Because those engines still suffer from almost all of the same issues.
Oh, and by the way, this is another Top 10 winner for Ward’s Best Engines awards. Go figures.
#3 Oldsmobile V8 diesel
Sticking with the train of diesel hate, let’s look at something old from Oldsmobile. This particular engine, the Oldsmobile V8 diesel engine, is one of the biggest turds to ever exist in a modern automobile.
Honestly, this engine is so bad that you partially or even fully blame it for ruining the chances of any diesel cars ever becoming popular in the states like they are in nearly any other part of the developed world. It’s that bad.
This engine was named the LF9, and it’s a common misconception that this engine was a compression-fuel conversion of the Chevy 350, but this is actually true. Rather, it’s a diesel conversion of the Oldsmobile 5.7-liter gasoline V8 engine that Oldsmobile had been using since the late 1940s.
Compared to that old gas engine, this new diesel had the same bore, stroke, bottom end, and all the same architecture, but it was about 25 lbs heavier due to the use of a beefier rotating assembly and revised cylinder heads.
At the time it was new, it outputs a whopping 120hp and 220lb-ft of torque. Every time you think an American-made V8 can’t physically have any less power, you’ll be blown away to find out that they somehow managed to make yet another engine with no power output.
It’s an absolute feat to engineer something with 5.7L of displacement and only 120hp, which gets even funnier because in later versions, Cadillac detuned them for improved fuel mileage and only output 105hp.
On the bright side though, the LF9 did offer decent fuel mileage during a time when gas prices were out of control relative to the average American’s income, and as such, it actually sold decently well.
But, problems quickly rode to the surface in the form of head gasket leaks, oil pan leaks, corrosion on the fuel injector pumps, water in the fuel, and problems with the three-speed automatic transmission that was pretty often paired with this engine.
Luckily, Oldsmobile put this engine out of its misery in 1985, but not after a class action lawsuit filed with the Federal Trade Commission that allowed owners to claim up to 80 percent of the original cost of the engine in the case of an engine failure.
Combine this with the return of cheap gas, and it makes sense why this engine went away.
#4 Cadillac V8-6-4
Now, this next engine I will applaud for its attempted innovation, and that’s the notorious Cadillac V-8-6-4 engine.
And what makes this engine so special is the fact that it had cylinder deactivation, which certainly wasn’t the first engine to do this, as it had successfully been done all the back in the early 1900s.
But those early engines were just that, early engines. Meaning, they kind of sucked like all engines from back then. Which is funny because Cadillac brought this cylinder deactivation technology back in 1981, and even then, it still sucked.
This system was standard on all 1981 Cadillac’s, and the technology actually came from Eaton; it was installed on the 1980 throttle body injected 6.0L V8, which at its core was just a destroked and debored 472.
This system was designed to shut off either two or four cylinders to increase fuel mileage, which you probably were able to figure out by the name of this engine.
The whole thing was controlled by Cadillac’s onboard computer, which used sensors to monitor engine speed, EGR, idle speed, intake manifold air pressure, coolant temp, and more.
If the computer sensed a sustained cruising condition, the computer would then signal a solenoid-activated blocker plate that physically moved the rocker arm, preventing the camshaft from opening the valve, making your 6.0L V8 a 4.5-liter V-6 or a three-liter V-4, on the fly.
If the system worked properly, you actually saw pretty decent fuel mileage, but that “if” is a big problem.
The big problem is that the software needed to run the entire system and monitor all those sensors wasn’t actually fast enough to process the information in time to make a decision. There were also press reports of the engine having noticeable hesitation and jolts when the engine deactivated cylinders.
And if this was in some sort of sh*tbox, maybe that wouldn’t matter, but this was a Cadillac. These types of problems are straight up not acceptable for their customers, and as such, many of these engines saw this system deactivated entirely, leaving the engine as a permanent V8.
That’s kind of funny. The cylinder deactivation got deactivated. Ha. Anyways. Couple those problems with the throttle injection system problems, and you’ve got a recipe for disaster.
#5 Ford Triton (5.4L and 6.8L)
Man, the Ford guys are gonna hate me after this video, but I’ve gotta do it. I’m sorry. The 5.4L and 6.8L Triton engines are next on the list.
But, to be fair, the 5.4L had a long run from 1997 to 2014, so it’s far from the worst engine on the list, but it has some notorious problems that are simply too funny not to talk about.
And that problem is spark plugs ejecting themselves out of the head in an attempt to enter orbit. No, seriously, those spark plugs went flying.
This whole thing is caused by a bad cylinder design, where the early two-valve 5.4L engine had an insufficient amount of threads for the sparkplug, and would either result in the threads coming out with the spark plug when they were changed or the force of compression and ignition literally shooting them out of the spark plug holes.
Funny story, way back before my YouTube days, I worked at a bicycle shop with my good friend Daniel. The shop had a work van with a Ford Econoline thing with 20″ or 22″ wheels, I don’t remember exactly. Regardless of that, it had the 6.8L Triton V8 in it, and we were driving in on the highway one time when one of the spark plugs ejected from a cylinder, and we drove it all the way back to the shop, which was about 30 minutes away.
Anyways, that whole spark plug issue was solved, at least to my understanding, when Ford introduced the three-valve version of the 5.4L. But, the introduction of the three-valve engine brought with it some problems with the timing chain system, which can result in the pistons and valves violently meeting together.
Outside those two major problems, the Triton engines aren’t actually that terrible, other than being gutless and making very little power in stock form.
#6 Toyota 3VZ-E V-6
And this last engine on the list might surprise you, as it’s a product from Toyota. That’s right. A Toyota engine made it onto my list of terrible engines, which is absolutely wild considering how many amazing engines they’ve built to this day.
Anyways, this particular engine is actually really close to being a good engine, but a few flaws put it on this list, and that’s the 3VZ-E.
On the surface, this is just another over-engineered product from Toyota. It’s supposed to be the perfect engine for the 4Runner, and it was the first engine larger than a four-cylinder to ever be offered in the 4Runner.
This is a 3.0L single overhead cam V6 outputting 150hp and 180lb-ft of torque. So, what example makes it an engine worth putting on this list? Head gaskets.
Of all the problems an engine can suffer from, this is problem one of the worst, but part of this issue seems to be clouded by the coolant system itself, which is very easy to have air bubbles stuck in and is actually often misdiagnosed as a head gasket issue.
That being said, it’s not clear if it’s a flaw with the cylinder heads or a defect in the gaskets Toyota originally used to assemble these engines when new.
As a side note, these little engines are also well known for being one of Toyota’s leakiest engines of the 1990s, but as a true Toyota guy would put it: “if it’s leaking oil, that means there is still oil in it.”
Honestly, though, outside the head gasket issue, this is actually a really solid engine, and I didn’t really want to put it on this list, but the show must go on.
Some honorable mentions I want to throw in here include the Mopar 2.2L for being a turd, the Land Rover 4.0L for slipping cylinder liners, and the 5.7L HEMI because they do nothing but knock their entire life. Seriously though, there are a lot of bad engines out there, but a lot of it is just subjective.